Measurement of charmless $B$ Decays to $ηK^*$ and $ηρ$

Abstract

We report measurements of branching fractions and CP asymmetries for $B \to ηK^*$ and $B \to ηρ$ decays. These results are obtained from a $414 {\rm fb}^{-1}$ data sample collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We measure the following branching fractions: ${\mathcal B}(B^0 \to ηK^{*0}) = (15.2 \pm 1.2 \pm 1.0)\times 10^{-6}$ and ${\mathcal B}(B^+\toηK^{*+}) = (19.3^{+2.0}_{-1.9}\pm 1.5)\times 10^{-6}$, where the first error is statistical and the second systematic. We also find a $2.7σ$ excess in the $B^+\toηρ^+$ mode and measure $\mathcal B(B^+\toηρ^+)= (4.1^{+1.4}_{-1.3}\pm 0.4)\times 10^{-6} <6.5 \times 10^{-6}$ at 90% confidence level. For $B^0 \to ηρ^0$ decays, we determine the upper limit $\mathcal B(B^0\toηρ^0) < 1.9 \times 10^{-6}$ at 90% confidence level. The partial rate asymmetries are ${\mathcal A_{CP}}(ηK^{*0}) = 0.17 \pm 0.08 \pm 0.01$, ${\mathcal A_{CP}}(ηK^{*+}) = 0.03 \pm 0.10 \pm 0.01$, and ${\mathcal A_{CP}}(ηρ^+) = -0.04^{+0.34}_{-0.32}\pm 0.01$.

9 pages, 6 figures, 3 tables, to be submitted to PRD, journal version of ICHEP06 conference paper hep-ex/0608034 with refinement of analysis